CB/OU/BR Cross Reference Matrix

Many RN 20th century publications were issued in three series.

CBs (Charge Books) were classified publications. TOP SECRET publications had a number which started with two leading zeros (e.g. CB 00314). SECRET publications had a single leading zero, while CONFIDENTIAL publications just had a straight number. If a TOP SECRET or SECRET publication was subsequently reduced in classification, this would be reflected by removing the appropriate number of leading zeros, however the number would remain unchanged if the document remained at least CONFIDENTIAL.

OUs (Official Use) publications were unclassified publications, which were given a serial number (e.g. OU 6308).

BRs (Books of Reference) were also unclassified publications, which were given a serial number (e.g. BR 862).

If a CB was declassified below CONFIDENTIAL, it would be recategorised as an OU or a BR and given a new serial number.

And then around the start of World War Two, the use of OU serial numbers was phased out, and many existing OUs (including some that had previously been CBs) were allocated BR numbers.

Thus, a single publication may over time have had three different serial numbers – which can make referencing and finding it difficult – as many references and catalogues will only list one of the numbers.

If a publication was issued in multiple volumes they might be indicated with sequential numbers (e.g. BR 825(1), BR 825(2)) or alternatively sequential letters (e.g. BR 961A, BR961B).

When a publication was reissued, it often retained the same number, and thus there will be multiple versions of the same document number differentiated by the year of publication. Sometimes (but not always) this was indicated by an appendage to the number (e.g. CB 01618L (1940) or BR 214/44).

This is an ongoing source of ambiguity (e.g. BR 1736(45) was the 45th volume in the BR 1736 series, however BR 224(45) was the 1945 issue of BR 224).

And after a publication was withdrawn from use, the number could then be reused for a completely unrelated publication.

A large number of CBs, BRs and OUs are held in The National Archives, however these are only a fraction of the total number issued. The publications in the National Archives have been allocated a File Reference number (e.g. ADM 234/526), and many researchers use these numbers as a proxy reference number for the publications.

The BR, CB or OU number is usually (but not always) included in the “Reference” field of the TNA Discovery database, however formatting is inconsistent, which makes it challenging to search for them. There are also numerous cases where either a single file contains multiple publications, or multiple copies of the same document are held on different TNA file numbers.

A final complicating factor is that many RN publications had long and convoluted titles (e.g. Handbook for ordnance, Q.F. 3.7 inch Howitzer, mark I on carriages, 3.7 inch Howitzer, marks I, II, III and IVP: land service). But library and archive catalogues often contain simplified titles, as do cross-references from within other RN publications – which can make searching by title hit and miss.

All of this can make tracking down a particular publication a challenge.

The table below was prepared to try and assist with this process from a number of angles:

• It provides a cross-reference between TNA file references and RN publications for all of the publications that I have been able to locate in Discovery.
• It provides a cross-reference between CB, OU and BR numbers for publications that were recategorised and renumbered.
• It identifies libraries/websites/publications which have copies of documents (although this is very lightly populated at present).

In order to be able to meaningfully sort the columns in the table, it has been necessary to standardise the formatting of the publication numbers, and in particular the leading “0”s from TOP SECRET and SECRET CBs have been removed.

The contents of this table were mashed together from a variety of sources, most of which contained incomplete, ambiguous, and sometimes erroneous data – so there will inevitably be errors and omissions in the table. It will always be a work in progress, and users are encouraged to let me know when they identify corrections or additions that can be incorporated.